1. Field of the Invention
This invention relates in general to an RF (radio frequency) communication devices, and more particularly to a radio frequency integrated circuit that can be used for a plurality of different frequency bands for reading and writing information in a non-contact manner using radio waves or electromagnetic waves.
2. Description of Related Art
In recent years, attention has been focused on a technology called radio-frequency identification (RF-ID) in which a person or an object is identified and managed using a radio frequency integrated circuit (IC) chip. A radio frequency integrated circuit (also referred to as an RF-ID tag, a radio IC tag, and the like) used in RF-ID communicates with a reader/writer using radio waves or electromagnetic waves, and can operate without having a battery by a technology in which power is transmitted from an antenna to an RFID chip.
In specifications of radio frequency integrated circuits, currently usable frequencies are four kinds of frequencies: a band of 135 kHz and below, the 13.56 MHz band, the 860-960 MHz band belonging to the so-called UHF band, and the 2.45 GHz band. The distance within which communication with a reader/writer is allowed varies depending on a frequency band used. Accordingly, frequencies need to be appropriately used depending on purposes as follows: for example, in individual commodity management and the like in which individual communication with each radio frequency integrated circuit is performed, a low frequency such as 13.56 MHz is used; and, in the simultaneous reading of radio frequency integrated circuits attached to a large number of products, the UHF band is used.
However, as described previously, a radio frequency integrated circuit obtains power from radio waves or electromagnetic waves used for communication with a reader/writer. Consequently, the operating frequency in the radio frequency integrated circuit depends on the frequency used for communication and is fixed. Accordingly, a user needs to select and use radio frequency integrated circuits having different frequencies depending on purposes such as the above-described individual commodity management and simultaneous reading. Further, in the case where radio frequency integrated circuits are used for a plurality of purposes in a certain product, it is necessary to prepare a radio frequency integrated circuit for each of frequencies corresponding to the purposes.
As described previously, the operating frequency of a radio frequency integrated circuit depends on the frequency at which IC chip can communicate. Accordingly, a user must appropriately select the type of a radio frequency integrated circuit depending on the purpose. This is a burden on the user. Further, in order to use radio frequency integrated circuits for a plurality of purposes, a plurality of radio frequency integrated circuits must be prepared depending on the purposes. This causes an increase in the cost of installing a system or the like using radio frequency integrated circuits.
If a single radio frequency integrated circuit can be used for a plurality of different frequency bands, there is no necessity to select the type of a radio frequency integrated circuit depending on the purpose or prepare a plurality of radio frequency integrated circuits. Additionally, a system using radio frequency integrated circuits becomes more convenient, and also becomes easy to install. In particular, if, in such a radio frequency integrated circuit, data at different frequency bands can be read by communication at different frequencies and restrictions can be placed on the reading and writing of information depending on which frequency is used, the system becomes much more convenient.
It can be seen that there is a need for a RF integrated circuit and integrated circuit module for reading and writing information in a non-contact manner using radio waves or electromagnetic waves.